The present invention relates to an arrangement for reinforcement at a longitudinally and/or areally extending structure or structural component by means of at least one lamina-like reinforcement disposed on the structure or structural component or masonry, slacked or prestressed, a structural component provided for support functions, as well as a method for reinforcing a structure or structural component.
For many years research and practice has been engaged in the subsequent reinforcement of structures, such as in particular ferroconcrete structures and masonry by applying additional reinforcement. The beginnings of this technique are described in J. Bresson, "Nouvelles recherches et applications concernant l'utilisation des collages dans les structures. Beton plaque.", Annales ITBTP No. 278 (1971), Serie Beton, Beton arme No. 116, and go back to the 1960s. Bresson directed his efforts in particular to the research of the composite tension in the region of the anchorages of steel laminae affixed by adhesion.
For approximately the past twenty years, existing structures, such as ferroconcrete structures, such as for example bridges, floor and ceiling plates, longitudinal girders and the like, but also nonreinforced masonry, can consequently be reinforced through subsequent affixing by adhesion of steel laminae.
The reinforcing of concrete structures and masonry by affixing steel laminae with, for example, epoxy resin adhesives, can be considered to be standard technique at this time. There are a variety of reasons which make reinforcement necessary:
increase of load capacity, PA1 change of static systems by removing, for example, bearing elements such as supports, or their support functions are reduced, PA1 reinforcement of structural components endangered by fatigue, PA1 increase of rigidity, PA1 damage of bearing systems or renovation of existing structures and of masonry, as well as PA1 faulty calculation or workmanship of the structures.
Subsequent reinforcement with steel laminae affixed by adhesion have been found to be useful on numerous structures such as is described for example in the following literature citations: Ladner, M., Weder, Ch.: "Geklebte Bewehrung im Stahlbetonbau" {Adhered armouring in ferroconcrete construction}, EMPA Dubendorf, Bericht No. 206 (1981); "Verstarkung von Tragkonstruktionen mit geklebter Armierung" {Reinforcement of bearing structures with adhered armouring}, Schweiz. Bauzeitung, Sonderdruck aus dem 92. Jahrgang, No. 10 (1974); "Die Sanierung der Gizenenbrucke uber Muota" {Renovation of the Gizen bridge across the Muota}, Schweiz. Ingenieur & Architekt, Sonderdruck aus Heft 41 (1980).
However, these reinforcement methods entail disadvantages. Steel laminae can only be supplied in short lengths which only allows application of relatively short laminae. Consequently, laminar stacks become necessary and thus potential weak points, cannot be avoided. The awkward handling of heavy steel laminae on the site can in addition lead to especially difficult problems in implementation techniques in the case of high structures or those difficult to access. Moreover, in the case of steel, even with careful corrosion protection treatment, the danger of lateral concealed rusting of the laminae, or the corrosion on the interface between steel and concrete exists which can lead to the detachment and thus the loss of reinforcement.
Accordingly, it was suggested in the publication by U. Meier, "Bruckensanierungen mit Hochleistungs-Faserverbundwerkstoffen" {Bridge renovation with high-performance fiber composites}, Material+Technik, Vol. 15, No. 4 (1987), and in the dissertation by H. P. Kaiser, Diss. ETH No. 8918 of the ETH Zurich (1989) to replace the steel laminae by carbon-fiber reinforced epoxy resin laminae. Laminae comprising this material are distinguished by a low bulk density, very high strength, excellent fatigue properties and outstanding corrosion resistance. It is thus possible to use, instead of the heavy steel laminae, light, thin carbon-fiber reinforced synthetic material laminae which can be transported virtually continuously in the rolled-up state to the construction site. It was found in practical determinations that carbon-fiber laminae of 0.5 mm thickness are capable of absorbing a tension force which corresponds to the yield force of a 3 mm thick FE360 steel lamina.
The stated carbon-fiber laminae have been found to be highly useful even when used for reinforcement of masonry in seismically hazardous zones. In Bericht {Report} 229 of the Eidgenossische Materialprufungs- und Forschungsanstalt (EMPA) {Swiss material testing and research institution}, Dubendorf, by G. Schwegler with the title "Verstarken von Mauerwerk mit Faservebundwerkstoffen in seismisch gefahrdeten Zonen" {Reinforcement of masonry with fiber composites in seismically hazardous zones} it is in particular suggested to reinforce existing masonry shear walls or walls in the facade region subsequently with fiber composite laminae. Therewith masonry can be decisively reinforced with respect to shearing and tension strength, compared to nonarmoured masonry. It is for example suggested therein to affix by adhesion! the reinforcement laminae diagonally and crosswise on a shear wall, such as a facade wall, and it was found that for increasing the shearing resistance the terminal lamina anchoring, for example in concrete plates, is critical.
Particular attention must be paid in all described cases to the shearing fractures formation in the concrete or the masonry, respectively. Shearing fractures lead to an offset on the reinforced surface which, as a rule, leads to the peeling or detaching of the reinforcement laminae. The shearing fracture formation is thus also a significant assessment criterion with respect to the load capacity of the nonreinforced structural component as well as also a potential detachment danger of the subsequently applied reinforcement laminae.
The International Patent Application WO93/20 296 describes a method by means of which structural components intended for bearing functions are reinforced against shearing forces thereby that the above cited reinforcement laminae are each pressed by means of clamping elements in the terminal region margin onto the structure in order to prevent their detachment. The laminae are disposed such that the distance from the lamina end to the support or the concrete plates disposed terminally at shearing walls is as small as possible. The anchoring zone must be dimensioned such that the lamina tension force can be anchored and the transfer of the force to a support or to the margin of concrete plates of a shearing wall is ensured.
But it was found in practice that anchoring the reinforcement laminae in the region of the supports is not always possible due to concrete beam haunches and shoulders which leads to an increase of the distance. Even when reinforcing shearing walls it is most often difficult and expensive to anchor the reinforcement laminae in the concrete plates disposed on these walls above and below. Furthermore, for reasons of handling at the construction sites it is advantageous if reinforcement laminae do not need to be excessively long which results automatically if, for example, when reinforcing bridges reinforcement laminae must each extend from support to support.